CA1327265C - Superconducting metal oxide compositions - Google Patents

Abstract

TITLE
SUPERCONDUCTING METAL OXIDE COMPOSITIONS
ABSTRACT
Compositions having the nominal formula Bi2Sr3-xYxCu2O?+y wherein x is from about 0.05 to about 0.45 and y is from about 0 to about 1 are superconducting.

Description

~ TITL~ 1 3 2 7 2 6 5 SUPERCON~UCTING M~TAL O~IDE COM20SITIONS

C~GROUND OF_T~E INVENTXON

rield of the I~vention This i~vention r~lates to ~
superconducting oo~position co~pri~ed of a crys~alline metal sxide pha~e ~n the ~i-Sr-~-Cu-O
system.

~ef~renc~s Bednorz and Muller, Z. ~hys~ ~64, 189 (1986), disclo~e a superconducting pha~e in the La-~a-Cu-O system with a supereonducting transition temperature of about 35 R. This disclosure was subsequently confir~ed by a nu~ber of investigators [see, ~or example, Rao and Ganguly, Current Science, 56, 47 (1987), Chu et al., Sci~nce 235, 567 (1987), Chu et al., Phys.
Rev. Lett. 58,.405 ~1987~, Cava et al., ~hys.
R~v. L@tt. 58, 408 ~1987), Bed~orz ~t al., ;~ Europhys. Lett. 3, 379 (1987)~. The uperconducting phase has been identified as the composition La~_l(3a,Sr,Ca)~CuO~_y with the tetragonal R~NiF~-type structure and with x typi~ally about 0.15 and y indicating oxyqen vaeancies.
: Wu et alO, Phys. Rev. Lett. 58, 908 ~1987), disclose a super:conducti~g phase in ~he Y-Ba-Cu-O system with a superconducting transition temperature of about 90 ~. Cav~ et al ., Phys . Rev. ~ett. 58, I676 (19R7), have CR-8683 identi~ied this ~uperconducting Y-~a-Cu-O phase ~o be orthorhombic, distorted, oxygen-deficient ~ .

~32~
perovskite Ysa~cu~o9 ~ where ~ i5 ~bout 2.1 ~nd present the powder x-ray diffr~ction pattern ~nd la~ti~e parameters.
c. Miohel et ~1., z. Phys. ~ -Condens~d Matter 6~, 421 (1987), d.is~lo~e a novel family of superconducting oxides in the ~i-Sr-Cu-0 ~yst~m with ~o~position clo~e to ~iaSrlCu20~ pure phas~ was i~solated fo~ the compo5~tion Bi25r2Cu207~. Th~ X-ray diffr~t~on pattern for this ~at~rial exhibit~ ~ome si~ilarity with that of perovskate and the electron diffraction p~ttern shows the perovskite sub~ell with the orthorhombic c~ll p~r~eters of a - So32 ~ (0.532 nm), b - 26.6 ~ ~2.56 n~) ~nd c . 48.8 ~ (4.~8 nm). The ~aterial ~ade ~om ultrapure oxides has a superconducting transition with a midpoint of 22 K as determined fro~
resistivity ~easurements and zero r~si~tanc~
below 14 K. The m~terial mate ~rom commer~ial grade oxides has a superconducting transition with a ~idpoint of 7 ~ .
- , H. Maeda et al., Jpn. J. Appl. Phys.
27, L209 (1988), disclose a superconducting oxid~
in the si-sr-ca-cu-o syst~ with the composition near BiSrCaCu20x and a superconducting transition t~mp~rature of about lP5 ~.

The co~monly assigned application, "Superconducting Metal Oxide Compositions and Process For Making Them", Canadian patent application serial no. 590,128, filed February 03, 1989, disclose supereonducting co~positio~s having the nominal formula ~iaSrbCacru30~ wherein ~ is from ~out 1 ~o about 3, b is from about 3/8 to about 4, G is from about 3/16 to about 2 ~nd x 8 (1.5 a + b ~ c y) where y is ro~ ~bout 2 to sbou~ 5, with ~h2 ~L3~7~
proviso that b + c is from about 3/2 to ~bout 5, ~aid co~positions h~ving ~up~rconducting tran~ition t~mperatur~s o~ about 70 X or higher.
It ~lso discloses the ~uperconduotin~ metal oxide phase having the ~ormula ~i2$r3_~Ca,Cu200~w wherein z is fro~ about 0.1 to about 0.9, preferably 0.4 ~o 0.~ ~d w is great~r than zero but les~ than ~bout 1. M. ~. Subra~ani~n ~t ~1., Science 239, 1015 (19B8) al~o diselose the E~i2 Sr3-8 C~l~ Cu2~ UE1lereonducll or.
T. ~amegai et al., ~pn. J. ~ppl. Phy~.
27, L1074 (1988), disol~se that Bi2Sr2YCu20~ 5 not a superconduetor but ls in~tead a se~iconductor.
A. Manthiram et ~1., Appl. Phys. ~ett~
53, 420 ~1988), disclose th~ results of a ~tudy of the compositionS ~i4 Sr3 Ca3 _ ~ Y~ l 6 ~ ~ Sa~lple8 with O.OSx~ are superconductors; those with x>1.25 are semiconductors. Tc remains almost constant at 86 ~ in the compositio~al range O<x<0.5 and then drops abrubtly and monotonically with x for x>0.5, extrapolating to zero ak x of about 1.15.

SU~MARY OF T~E I~VENTION
This invention provides novel superconducting compositions having the nomin~l formula ~i~Sr3~xY~Cu20~y wherein x is fro~ about 0.0~ to about Q.45 and y is f ro~ ~bout O ta about 1. ~h2 midpoint of th~ superconductivity ~or transition these compositions is at least 60 ~.

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~ IG. 1 shows a plot o~ ~he ~lux excluded by ~ composition o~ this invention ~s ~unction of t~mperature.

DETAIIIED DESCRIPTIO~ OF T~E: INVENTION
.
The ~uperconducting co~positions o~
thi s invention can be prepa~ed by ~.he following process. Quantities of the oxide reactants or ~heir precursor are chosen wi~h th~ a~o~ic r~io of Bi:Sr:Y:Cu o~ 2:3-x:x:2 where;n x is ~ro~
about 0.05 to about Q.45 and ~ixed, for example, by grinding the~ toqet~er in a ~ortar. The ~ixed powder may then be heated disectly or it can ~e first ~ormed into a pellet or oth~r sh~ped object and then heated. The powder os pellet is placed in a crucible made of a non-reacting metal such as gold. The crucible is then placed in a furnace and heated to about 850C to about 925QC
for about 3 hours or more. The power to the furnace is then turned off and the crucible is furnace-cooled to ambient temperature, about 20C. The cru~ible is then re~oved from the furnace and the blac~ product secovered.
When the quantities of the r~ac~ants are chosen such that x is from about 0.3 to about 0.4, the product is single phase.
Superconducting compositions of this invention corresponding to values o~ x less than about 0.3 are comprised-o~ this superconducting phase.
superconductivity can be confir~@d by observing magnetic ~lux exolusion, i.e., th~
M~i~sner effect. This effect can be ~ea~ured by - ~he ~ethod de5cribed in an art;cle ~y E. ~o~ur~
~nd B. Fisher in ~hysical ~eview ~, 360 5586~1987).

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.. . .

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1327~.3 The super~onducting eompositions of this invention can be used to conduet currsnt extr~mely ~fficiently or to provide a ~agnetic field or ~agnetic i~aging or ~edic~l puFpo~es.
Thus, by cooling the composition in the Xor~ cf a wire or bar to a temperatur~ b~low the superconducting transition te~p~rature Te 1~ a ~anner well known to those in this field ~nd initi~ting a ~low o~ eleet~iGal curr~nt, one ~n obtain such ~low without any electrical ~esistive 1O6ses. ~o provide exeeptionally high magnetic fi~lds with ~inimal power losses, the wire ~entio~ed previously could be wound to form coil whlch would be cooled below Tc before inducing any current into th~ ~oil. Such fi~lds can be used to levitate objects as large as rail-road cars. These superconducting compositions are also useful in Josephson devices such as SQUIDS (superconducting quantum interference devices) and in instruments that are based on the Josephson effect such as high speed ~ampli~g circuits and voltage standards.

EXAMPLES OF THE INV} :NTI ON
EXAMPLES 1-4, ESXPERIMENTS A-B
Compositions corresponding to x ~ 0.1, 0.2, 0.37 0.4, 0.5 and 0.8 in the for~ula Bi2Srl ~Y~Cu2Oe,y were prepared by grinding in an agate mortar for about 30 minutes the quantities of ~i203, SrO2, Y203, and CuO shown in Table I
~or each Example and ~xperiment. ~ellets, 10 ~m in dia~eter a~d about 3 ~m thick, were pre~ed ~rom this mixed powder for ~ch co~positi~nO In ~ach the pellets were placed in a gold c~uc~ble.
The crucible was placed in a furnaee and heat~d at a rate of 5C per minute to 9000C ~nd th~n S

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; ~. . . . -.

13272~
held at 900C for 24 hours. Power to the ~urnaee was then shut of~ and the crucible was allowed to coo~ to room temperature in the furnac~. The crucible was then removed rom the furnace ~nd the blac~ produet was r~covered.
X-ray powder di~fraetion pattern~ of ~he product o~ ~ach Ex~ple ~howed that wh~n x is 0.3 and 0.4, the produ~t ~ essentially ingle phase. Wh~n x ~s 0.1 ~nd 0~2, the product contains other phases as we~l as the ph~se de~ected when x $s 0.3 and 0.4. ~he X-~y data were indexed on a psu~dot~tr~gon~l unit oell an~
the lattice para~eters are given ~n Table I~o Meissner ~ect ~easure~ents were carried out and the temperature of the midpoint of the ~uperconductivity transition is shown in Table II. ~he results for Exa~ple 3, x ~ 0.3, are shown in Fig. 1 where the flux exclusion is plotted as a function of te~pe~ature. The products of Experiments A and ~, x ~ 0~5 and x - 0.8 were not superconducting ~t temperatures as low as 4.2 ~.

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TA~LE
Exam. x Eli2 3 2 SrO;~ 2 Y2 ~l ~a CuO g 0 . 1 1 . 3979 1 . 0407 0 . ~339 0 . 4772 2 0.2 103979 1.~048 0.0677 0.~772 3 ~3 5.5915 3.8750 ~.4065 1.90~0 4 9.4 3.7277 2.4881 ~.3613 1.2726 Exper. x ~i O ,~ Sr9 51 Y t~ .2 2 3 _2 _a 3 A 0 . 5 3 . 72~7 2 . 3924 0 . 4516 1. 2726 E~ O . 9 3 . 7277 2 . 1053 0 . 7226 1 . 2726 TA~E
Latti~e Paraglle~ers Exam . a ( rlm ~ e ~ n~ , ( R ) 5 . 44 30 . 85 70 2 5 . ~3 30 . a5 70 3 5.44 30.81 65 4 5.45 3~.66 60 ' Exper. a (nm) c (rlm) Tc ~R) A 5.46 30.60 ---~.~5 ~0.27 --~ ,

Claims (6)

1. A superconducting composition having the nominal formula Bi2Sr3-zYxCu2O3+y wherein x is from about 0.05 to about 0.45 and y is from about 0 to about 1, said composition having a superconducting transition temperature of at least 60 K.

2. A superconducting composition as in Claim 1 wherein x is from about 0.3 to about 0.4, said composition being essentially single phase.

3. A superconducting composition as in Claim 2 wherein x is about 0.3.

4. A superconducting composition as in Claim 2 wherein x is about 0.4.

5. A method for conducting an electrical current within a conductor material without electrical resistive losses comprising the steps of:
cooling a conductor material composed of a composition of Claim 1 to a temperature below the Tc of said composition;
initiating a flow of electrical current within said conductor material while maintaining said material below said temperature.

6. An improved Josephson-effect device wherein the superconductive material comprises the composition of Claim 1.